29Si MAS n.m.r. of aluminosilicate sodalites: Correlations between chemical shifts and structure parameters

Abstract

The 29 Si n.m.r. chemical shifts of 16 sodalites of the general composition M 6+x [SiAlO 4 ] 6 A x ·nH 2 O (M = alkali metal cation, A = OH − , anion) cover a range of more than 20 ppm and show linear correlations with the SiOAl bond angles and the lattice constants. As a result of the different steric and coordination requirements of the various nonframework constituents, bond-angle variations between 126 and 160° occur, and these can be calculated directly from the chemical shift data. The 29 Si chemical shifts and the average SiOAl bond angles of Si(4Al) environments in several other zeolites also fit the same type of correlation that has been established here for the sodalites.